Wolf-Rayet wind structure and optical variability

Details Wolf-Rayet wind structure and optical variability Wolf-Rayet wind structure and optical variability

May 2000

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2000a%26a...357..233l&link_type=abstract

Astronomy and Astrophysics, v.357, p.233-240 (2000)

Astronomy and Astrophysics

Astrophysics

12

Polarization, Stars: Mass-Loss, Stars: Variables: General, Stars: Wolf-Rayet, Stars: Winds, Outflows

Scientific paper

Results are presented on the expected variability of Wolf-Rayet (WR) stars in broad-band optical polarimetry and photometry, and in emission line profiles, due to an inhomogeneous random distribution of blobs in spherical geometry. Time dependent 3-D simulations are carried out with blob ejection random in time and direction, and the radiation properties are evaluated in the optically thin limit. In contrast with previous purely statistical analyses, inclusion in the present treatment of a beta velocity law and stellar occultation effects can yield results consistent with observations of the mean polarisation bar p and the ratio R=sigma_p /sigma_phot of polarimetric to photometric variability. Such consistency puts constraints on model parameters. Indeed by considering combinations of the three observables sigma_p , sigma_phot , and bar p it is possible to infer reasonably good estimates of three wind-blob parameters - the beta of their velocity law, the total mass loss rate dot M in blobs and the total number N of blobs emitted per wind flow time ({R_*}/{v_{\infty}}), provided the blobs are reasonably localised in angular and radial extent. It is found that typical data requires beta >= 1.5, {cal N} ~ 20-50 and dot M ~ 10-4 M_\odot/year. The N estimate is consistent with the number of observed narrow features on emission lines. Smaller values of beta are excluded. This improved model shows that data do not after all demand very dense blobs as previously suggested, and offers a valuable diagnostic of WR wind structure parameters.

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